Convert a difftime to a number in a time unit

pknca_difftime_to_unit() expresses a duration in the time unit of an analysis, such as a collection duration that is the difference of two date-times, so that it can be used with PKNCAconc() and PKNCAdose() times and durations given in that unit. The same conversion turns date-times and difftime durations into numbers in pk.nca().

Usage

pknca_difftime_to_unit(x, unit)

Arguments

x

A difftime vector (NA values stay NA, and a zero-length vector gives a zero-length result)

unit

The time unit to express x in, a single string such as "hr" or "day"

Value

A numeric vector the length of x: the duration in unit, with no unit or other attributes

Details

A difftime of any of its units (seconds, minutes, hours, days, or weeks) is converted exactly, through seconds. unit may be any time unit that the units package knows, such as "hr", "min", "day", or "week". Hours ("hr") need no conversion, so they work without the units package; every other unit needs the units package installed, which stops with an error from rlang if it is missing.

To convert a number that is not a difftime, say its unit first with base::as.difftime().

Errors

An x that is not a difftime stops with the class pknca_error_difftime_not_difftime, because a plain number has no unit to convert from. A unit that is not a single string, or that is not a time unit the units package can convert hours to, stops with the class pknca_error_difftime_unit.

Examples

# Hours need no conversion beyond the difftime's own unit
pknca_difftime_to_unit(as.difftime(90, units = "mins"), unit = "hr")
#> [1] 1.5
# Any other unit needs the units package
pknca_difftime_to_unit(as.difftime(36, units = "hours"), unit = "day")
#> [1] 1.5
# The difference of two date-times
start <- as.POSIXct("2026-10-05 08:00:00", tz = "UTC")
end <- as.POSIXct("2026-10-05 20:30:00", tz = "UTC")
pknca_difftime_to_unit(difftime(end, start), unit = "min")
#> [1] 750